An examination of the strain-induced orientation of hard segment domains in 4,4′-methylenebis(phenyl isocyanate)-based polyurethane-diacetylene segmented copolymers

✍ Scribed by P.T. Hammond; R.A. Nallicheri; M.F. Rubner

• Book ID: 103951143
• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 592 KB
• Volume: 126
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(90)90134-o

✦ Synopsis

The orientation of hard segments during tensile deformation in diacetylene containing polyurethanes was examined using visible dichroism. The visible spectra of 4,4'-methylenebis(phenyl isocyanate)-poly(tetramethylene oxide)-based polyurethane films containing fully extended polydiacetylene chains in their hard domains were measured with polarized light in the stretched and relaxed state. It was found that the hard segments were prefentially oriented normal to the direction of stress at strain levels up to about 500%, indicating that the long axis of the hard domains was orienting parallel to the stretch direction during the deformation process. The orientation of these domains was relatively reversible, with only small to moderate degrees of residual orientation present in the relaxed state of the polymer. The results also showed evidence of significant stress levels in the hard domains oriented in the stretch direction at strains as low as 40%, whereas hard'domains in the transverse direction are essentially load free except at very high strains. The hard domains appeared to remain structurally intact following strains of at least 300%-400%; however, at strain levels higher than 500%, there is some evidence of hard domain disruption.